---
name: "strcasecmp"
section: "3p"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/strcasecmp/3p"
---

# strcasecmp(3p)

case-insensitive string comparisons

## PROLOG

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

## NAME

strcasecmp, strcasecmp\_l, strncasecmp, strncasecmp\_l — case-insensitive string comparisons

## SYNOPSIS

```
#include <strings.h>
```

int strcasecmp(const char \**s1*, const char \**s2*); int strcasecmp\_l(const char \**s1*, const char \**s2*,\
     locale\_t *locale*); int strncasecmp(const char \**s1*, const char \**s2*, size\_t *n*); int strncasecmp\_l(const char \**s1*, const char \**s2*,\
     size\_t *n*, locale\_t *locale*);

## DESCRIPTION

The *strcasecmp*() and *strcasecmp\_l*() functions shall compare, while ignoring differences in case, the string pointed to by *s1* to the string pointed to by *s2*. The *strncasecmp*() and *strncasecmp\_l*() functions shall compare, while ignoring differences in case, not more than *n* bytes from the string pointed to by *s1* to the string pointed to by *s2*.

The *strcasecmp*() and *strncasecmp*() functions use the current locale to determine the case of the characters.

The *strcasecmp\_l*() and *strncasecmp\_l*() functions use the locale represented by *locale* to determine the case of the characters.

When the *LC\_CTYPE* category of the locale being used is from the POSIX locale, these functions shall behave as if the strings had been converted to lowercase and then a byte comparison performed. Otherwise, the results are unspecified.

The behavior is undefined if the *locale* argument to *strcasecmp\_l*() or *strncasecmp\_l*() is the special locale object LC\_GLOBAL\_LOCALE or is not a valid locale object handle.

## RETURN VALUE

Upon completion, *strcasecmp*() and *strcasecmp\_l*() shall return an integer greater than, equal to, or less than 0, if the string pointed to by *s1* is, ignoring case, greater than, equal to, or less than the string pointed to by *s2*, respectively.

Upon successful completion, *strncasecmp*() and *strncasecmp\_l*() shall return an integer greater than, equal to, or less than 0, if the possibly null-terminated array pointed to by *s1* is, ignoring case, greater than, equal to, or less than the possibly null-terminated array pointed to by *s2*, respectively.

## ERRORS

No errors are defined.

*The following sections are informative.*

## EXAMPLES

None.

## APPLICATION USAGE

None.

## RATIONALE

None.

## FUTURE DIRECTIONS

None.

## SEE ALSO

*wcscasecmp()*

The Base Definitions volume of POSIX.1‐2017, ***\<strings.h\>***

## COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting\_bugs.html .